Bacteria

• Microbiology is the study of organisms that are too small to be seen clearly by the unaided eye, known as microorganisms or microbes
• Microorganisms include viruses (non-cellular), prokaryotes (bacteria/archaea), and eukaryotes (protists, algae, fungi)
• Most microorganisms carry out their life processes independent of other cells
• Microorganisms exist in populations in nature as mixed populations interacting with each other and with other organisms through competition and cooperation
• Most of the biomass on earth is microbial, with an estimated total number of microbial cells on earth being 5 x 10^30 cells
• Infectious diseases are caused by pathogens and are still a major cause of death in lower-income countries
• Control of infectious diseases involves vaccination, antibiotics, personal hygiene, and drastic control measures
• Microorganisms can be both beneficial and harmful to humans, with most microorganisms being beneficial
• Food materials that benefit from microbiological activity include yogurt, cheese, vinegar, sauerkraut, certain sausages, beer, and wine
• Microbes can cause problems in food by leading to food spoilage, foodborne diseases, toxins, and poisoning
• Bacteria are a type of biological cell that constitute a large domain of prokaryotic microorganisms
• Archaea are similar to bacteria in size and simplicity of structure but differ in molecular organization, lacking peptidoglycan cell walls
• Cell sizes: Viruses (0.01-0.2 μm), Bacteria (0.2-5 μm), Eukaryotes (5-100 μm), Yeast (5-10 μm), Algae (10-100 μm), Protists (50-1000 μm)
• Eukaryotic cell structure includes the endoplasmic reticulum, cytoplasmic membrane, cell wall, nucleus, mitochondrion, Golgi apparatus, ribosomes, and chloroplast
• Functions of the bacterial cell membrane include barrier function, selectively permeable barrier, site of respiration and photosynthesis, and energy conservation
• Bacterial cell wall determines and maintains the shape of bacteria and protects the cell from osmotic lysis
• Bacteria are divided into two major groups based on their response to the Gram stain: Gram-positive and Gram-negative bacteria
• Components external to the cell wall include capsule, which provides protection from host defenses and harsh environmental conditions, and fimbriae and pili for recognition and attachment to surfaces
• Patterns of flagella arrangement include polar flagellum, monotrichous, amphitrichous, lophotrichous, and peritrichous
• Bacterial cytoplasm contains ribosomes, nucleoid, cellular inclusions, macromolecules, organic molecules, and inorganic ions
• The nucleoid is the irregularly shaped region where the chromosome is located, and plasmids are small, closed circular DNA molecules that exist and replicate independently of the chromosome
• Cellular inclusions in bacteria include granules of organic or inorganic material reserved for future use, such as glycogen, poly-β-hydroxybutyrate, polyphosphate granules, and sulphur granules
• Endospores are made by some Gram-positive bacteria and have advantages such as surviving for long periods under unfavorable conditions
• Differences between prokaryotic and eukaryotic cells include cell size, presence of a nucleus, number of chromosomes, mitosis, presence of membranous organelles, cell wall composition, ribosome types, presence of cilia and flagella, among others
• Give some examples of newly emerging disease

  COVID-19, Influenza, Monkey pox, Nipah
• what are the 3 domains?

  Eukaryote, archaea, bacteria
• Describe a eukaryote

  • An organism that consists of one or more cells each of which has a nucleus and other well-developed intracellular compartments.
  • Eukaryotes include all organisms except bacteria, viruses, and certain (blue-green) algae which, by contrast, are prokaryotes.
  • Eukaryotes include fungi, animals, and plants as well as some unicellular organisms.
• Describe the bacterial domain

  • Bacteria are a type of biological cell.
  • They constitute a large domain of prokaryotic microorganisms.
  • Typically, a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals.
  • Bacteria were among the first life forms to appear on Earth and are present in most of its habitats.
• Describe the characteristics of Archaea

  • the presence of characteristic tRNAs and ribosomal RNAs
  • the absence of peptidoglycan cell walls, with in many cases, replacement by a largely proteinaceous coat
  • the occurrence of ether linked lipids built from phytanyl chains
  • in all cases known so far, they occur only in unusual habitats. 
• what is the importance of cell volume


  •Higher surface/ volume ratio of smaller cells leads to faster rate of nutrient exchange compared to large cells

  •Smaller cells = faster growth

  •Evolution/mutation rates, more cells/growth > more mutations may lead to greater evolutionary possibilities
• Whats the role of ER


  protein glycosylation, membrane factory, lipid synthesis)
• what is the role of the golgi?


  modifies, stores, routes products of the ER
• whats the role of the chloroplast

  photosynthesis
• what are the components of the bacterial cell

  Nucleoid, ribosome, inclusions, capsule/slime, Flagellum, s-layer, cytoplasmic membrane
• Describe a gram-positive cell wall

  wall-associated protein, teichoic acid, lipoteichoic acid, peptidoglycan, cytoplasmic memb
• Describe a gram-negative cell wall

  Lipopolysaccharide (LPS), porin, periplasm, lipoprotein
• describe peptidoglycan structure

  •Peptidoglycan only found in Bacteria.•Cell wall antibiotics such as Penicillin prevent cell wall formation and are bacteriolytic•LYSOZYME breaks G-M  bonds.  ‘bursts the cell’•Defence against bacteria•

  G = N-Acetylglucosamine

  M = N-Acetylmuramic acid

  MG polymer chains linked via peptide bridges
• why does not lysozyme lyse archaea

  they lack peptidoglycan
• why doesn't penicillin kill archaea

  they have a variety of cell walls including pseudo-peptidoglycan
• what is an amphitrichous flagellum

  one flagellum at each end